I think if you disconnect the oil pressure switch and start the engine the “check gauges” light will light up.
@"Tester I don’t believe the check gauges will come on if the oil pressure stepper motor is defective
If the oil pressure sender/switch is fine, and the pcm sees proper oil pressure, it won’t know the stepper motor is faulty
I have observed when a GM stepper motor is faulty, if you hook up a scan tool, you will see what the module sees, not what the cluster is displaying to the driver
You should inform @“Barkydog” of this procedure.
Then they can let you know if they have such a scan tool?
Tester
Any scan tool that is GM oe-level will do, in other words Snap on, Matco, or the higher level OTC, to name a few
We’ve had several gm vehicles with bad stepper motors in the shop. Occasionally, it’s the speedometer stepper motor that is bad
But there is no check gauges light on
When I hook up the scanner, I see the vehicle speed just fine. The PCM doesn’t know the stepper motor is faulty. Neither does the cluster, for that matter
@Barkydog After the engine’s awhile, does the oil pressure gauge indicate a normal value?
Put a mechanical oil pressure gauge on it, and start it up cold . . . what’s the mechanical gauge showing?
@db4960 If the oil pressure gauge is a stepper motor failure just one more stepper motor to fix, but I am unsure it is a stepper motor that controls the oil pressure gauge. I have seen posts on both sides of the fence, if it is a stepper motor I can skip the pressure switch, but varying accounts call it an analog gauge controlled by the brains of the car.
Missing the days when you could trace wires to fix problems.
The problem is 1 time I start no reading on the gauge for the total drive, a day later 40 psi reading on startup, hit or miss.
Replace the switch/sender first . . . it should be relatively inexpensive
If that fixes the problem for good, your troubles are over
if not, you’ll have to continue sleuthing
I finally got around to checking my schematics, the I6 is a switch to the PCM. Depending on your year, it could be either a 2 way (0, 40psi) or 3 way (0, 40, 80psi) switch. The PCM calculates a value in between those switch values based on conditions and adjusts the gauge to match. In other words, a complete fake gauge.
Simple enough to back probe either the switch or PCM to see if the switch is functioning when the gauge reads zero…
another thought- the TB uses audible alarms for error conditions. If the system is not alarming when it reads zero, it is probably the gauge. You could test this by unplugging the switch with the engine running and see if it alarms.
I took it to a shop, they scanned the cluster first and it has a bad circuit board. I figured if it was the switch a check gauges light and limp mode would be kicking in. The light kicks on at 12 or 14 psi depending on who you believe.
Got the cluster scanned, bad circuit board in the cluster, I just do not think it is worth the $605 to replace and reprogram the cluster to get a fake gauge working.
Since I will probably drive it until a major expense causes me to upgrade loss of trade in value is not a concern. Thanks All!
Rock Auto has a replacement cluster for $180.00.
https://www.rockauto.com/catalog/moreinfo.php?pk=2347126&cc=1412277&jnid=499&jpid=1
Tester
@tester that is doable, THANKS!
Gets a little scary but they seem to have their act together as far as reprogramming.
Wonder why they show one going 5mph @ 400 rpm!
I’ve heard of people just re-soldering all the solder joints on cluster printed circuit boards, sometimes it works.
Sounds like an idea, but with one failed stepper motor for the speedo, and one intermittent not liking to work in the cold tach, and intermittent oil pressure gauge based on circuit board, not motor I will go rebuilt, hope others find your post helpful @GeorgeSanJose
@Barkydog I had no idea your entire cluster was so “fragile”
It sounds like most/all of the problems are due to the stepper motors
How have you been estimating your speed . . . go with the flow?
@db4960 My gps calculates speed, and also shows posted limits, a nice feature, your speed indicator turns red when going over the posted limit.
Nice